For some heat pump mini-split systems, the same conductor is used for the proprietary data communication signal (i.e. 12~24VDC) with a power voltage of 208~230 from the outdoor unit (heat pump) to the indoor unit (fan coil). See Mitsubishi Electric's M and P Series systems, aka, Mr. Slim.

I would like to read an explanation of how both DC and AC voltage can share the same wire.

I am guessing it may be RF and AC.
Can't say for the Mini split you speak of.
But the Outdoor Antennas with a Preamp and Power supply, use chokes and capacitors to join and separate the AC voltage and the Amplified RF signal.
That would be my guess.
I will look into those models, Mostly they have about 5 conductors between the 2?

This best explained using a AM Radio Signal Wave.

A carrier wave (DC signal) is generated at a specific freq. Next, the AC sine wave is imposed on the Carrier signal.

The resulting distorted signal is transmitted. When you tune to a station on the radio, the receiver in the radio strips away the carrier signal, leaving the AC signal for the radio to broadcast.

The same principal exists for your question. The imposed DC signal is stripped away and routed to wherever it is supposed to go and the AC is left to do what it is needed for.